Systematic Study on Morphological, Electrochemical Impedance, and Electrocatalytic Activity of Graphitic Carbon Nitride Modified on a Glassy Carbon Substrate from Sequential Exfoliation in Water

Abstract

Several researchers have synthesized graphitic carbon nitride (GCN) from various precursors and attached it to electrode substrates after exfoliation under different conditions and have reported inconsistent data on electrochemical impedance, electroactive surface areas, and electrocatalytic activity. Thus, the present study aims to study the same systematically in addition to morphology after modifying GCN on the GC substrate from different exfoliation times in water assisted by sonication. The GCN was prepared from urea by bulk condensation pyrolysis and then attached to the GC substrate by drop casting to study its morphology, electrochemical impedance, and electrocatalytic activity with respect to exfoliation. The SEM image of a GCN-modified GC plate after 15 and 30 min of exfoliation shows bulky structure whereas thin sheets of GCN were noticed after 120 min of exfoliation. On the other hand, broken sheets were observed when GCN was coated from beyond 120 min of exfoliation. The electrochemical impedance studies show that the charge transfer resistance (R CT) of GCN modified from 15 and 30 min of exfoliation was higher than that for the bare GC electrode. However, it started to decrease while increasing the exfoliation time, and 1.8 kΩ was obtained after 120 min of exfoliation. The R CT value was again increased to 3.2 and 5.0 kΩ for GCN coated after 150 and 180 min of exfoliation, respectively. The electroactive surface area (EASA) of GCN modified by 15 and 30 min of exfoliation was less than that of the bare GC electrode, whereas it was 3.8-fold higher for GCN coated from 120 min of exfoliation. The electrocatalytic activity of the GC electrodes modified with GCN was then tested by studying ascorbic acid (AA) and dopamine (DA) oxidation and reduction of hydrogen peroxide (HP). Among the different exfoliation times, GCN modified from 120 min of exfoliation displayed the highest electrocatalytic activity toward AA, DA, and HP. This was attributed to its higher EASA and lower charge-transfer resistance.

Electrocatalytic Hydrogen Evolution Using A Molecular Antimony Complex under Aqueous Conditions: An Experimental and Computational Study on Main‐Group Element Catalysis

“…The current density of −0.3 mA/cm 2 at −1.4 V vs. NHE (current density of SbSalen is −30.7 mA/cm 2 at the same potential) suggests that the catalytic activity is from the SbSalen heterogenized on the carbon paper. When the electrochemical impedance of a carbon paper electrode with SbSalen was compared with the impedance of a bare carbon paper electrode (Figure S7), there is a significant decrease in the charge transfer resistance (R CT ) when the carbon paper was modified with SbSalen , suggesting that the modified electrode is more conductive and therefore supports the higher catalytic activity of SbSalen compared to the blank carbon electrode [38] . An additional control experiment using heterogenized H2Salen (Figure S8) produced less favorable results (74 % H 2 Faradaic efficiency and −2.9 mA/cm 2 at −1.4 V vs. NHE) than those of the blank, which suggests that the antimony center is responsible for most of the high activity of SbSalen .…”

“…When the electrochemical impedance of a carbon paper electrode with SbSalen was compared with the impedance of a bare carbon paper electrode (Figure S7), there is a significant decrease in the charge transfer resistance (R CT ) when the carbon paper was modified with SbSalen, suggesting that the modified electrode is more conductive and therefore supports the higher catalytic activity of SbSalen compared to the blank carbon electrode. [38] An additional control experiment using heterogenized H2Salen (Figure S8) produced less favorable results (74 % H 2 Faradaic efficiency and À 2.9 mA/cm 2 at À 1.4 V vs. NHE) than those of the blank, which suggests that the antimony center is responsible for most of the high activity of SbSalen. To determine whether antimony alone can catalyze the HER under the same conditions, an electrode with SbCl 3 was prepared and CPE was performed at the same potentials (Figure S9).…”

Optimizing dicyandiamide pretreatment conditions for enhanced structure and electronic properties of polymeric graphitic carbon nitride

“…Specifically, a sharp absorption peak at 806 cm À1 represents the breathing mode of triazine rings. 50 The peaks between 1200-1650 cm À1 correspond to the C-N and CQN stretching vibration modes. The broad peaks between 3000 and 3300 cm À1 can be assigned to the stretching vibration of N-H/O-H bonds associated with uncondensed amino groups or surface adsorbed water.…”

Surface Physicochemistry Modification and Structural Nanoarchitectures of g‐C3N4 for Wastewater Remediation and Solar Fuel Generation

“…[166] Meanwhile, in another study, Gowri et al used different sonication times (15,30,60,120,150, and 180 min) to evaluate its effect on the surface chemistry of g-C 3 N 4 (GCN). [167] Various morphologies were obtained according to the sonication times. The bulk structure of GCN was altered to nanosheets structure as the exfoliation time increased up to 120 min.…”